1. (Field of the Invention)
The present invention relates to an information pattern discriminating apparatus for determining a product based on a signal indicative of the information pattern, which is detected by a sensor with respect to such product while one of the product and the sensor is moved relative to the other of the product and the sensor. Particularly, the present invention relates to the information pattern discriminating apparatus capable of accommodating a time deviation attributable to the movement of one of the product and the sensor relative to the other of the product and the sensor.
2. (Description of the Prior Art)
In the conveyor line for sorting products, the information pattern discriminating apparatus has hitherto been used for determining the products one by one based on results of detection performed by a sensor with respect to the by a sensor with respect to theach of those products. With this conventional information pattern discriminating apparatus, while the products are successively transported from one processing station towards another processing station, the sensor detects the information pattern specific to each of the products, such as an information pattern regarding the shape of each product or an information pattern uniquely applied to each product, so that each of the products can be identified on the basis of the result of detection performed by the sensor.
More specifically, by way of example, the conventional information pattern discriminating apparatus includes a photosensor for detecting an information pattern, for example, a black-and-white grid pattern, made up of an array of black areas and an array of white areas alternating with the black areas as shown in FIG. 9A. The black-and-white grid pattern is printed on a label applied to each of the products to be identified. When in operation, the photodetector outputs an ON signal when it detects the white areas of the information pattern, but an OFF signal when it detects the black areas of the information pattern, to eventually provide an ON-OFF pattern signal for each of the products. This ON-OFF pattern signal is subsequently compared with a standard ON-OFF pattern signal indicative of an acceptable sound product and, if the ON-OFF pattern signal detected by the photodetector coincides with the standard ON-OFF pattern signal, an OK determination is made (i.e., the product detected is determined as acceptable), but if the ON-OFF pattern signal detected by the photodetector does not coincide with the standard ON-OFF pattern signal, an NG determination is made (i.e., the product detected is determined as unacceptable).
In such case, in the conventional information pattern discriminating apparatus, as shown in FIG. 9B, using a plurality of, for example, two, photosensors 1A and 1B capable of detecting such an information pattern as shown in FIG. 9A, an internal counter is counted up in dependence on change of ON and OFF to manage the state, and the ON-OFF pattern signal (information pattern signal) is obtained by adding the length of time required for the count of the internal counter to change and the ON-OFF state of the photosensor 1B when the ON-OFF state of the photosensor 1A changes. Since the ON-OFF pattern signal given by the standard product (acceptable sound product) is used as the standard ON-OFF pattern signal with which the ON-OFF pattern signal given by the product being detected is determined, the apparatus must store it and, with the use of, for example, a programmable logic controller (PLC), it is necessary to convert it into a program before it is inputted.
Since where the PLC is used, the ON-OFF pattern differs from one product class to another, the ON-OFF pattern that differs from one product class being manufactured to another must be converted into a program, requiring cumbersome and time-consuming procedures. For this reason, a data processing apparatus has been suggested in, for example, the Japanese Laid-open Patent Publication No. 9-273923, in which an acceptable sound product is transported by a conveyor and is detected by a photodetector to provide a standard signal waveform indicative of the acceptable sound product, so that even if the product class change, an input signal waveform given by a product can be compared with the standard signal waveform to thereby determine the produce so detected.
With this data processing apparatus, since no accurate discrimination is possible in the event that an object being transported by the conveyor deviates in position by an undulated movement of the conveyor and the position of the object changes for each measurement, the deviation in position of an analog input signal waveform relative to the standard signal waveform must be determined so that a process can be executed to move the input signal waveform by a quantity corresponding to the deviation in position.
However, since the above mentioned data processing apparatus merely move the position of the input signal waveform in a quantity corresponding to the deviation in position relative to the standard signal waveform, the data processing apparatus is incapable of accommodating instantaneous change of the speed of the conveyor, such as caused by a vibration such as occurring upon jerky movement of the conveyor itself and/or abrupt placement of a product on the conveyor, or deviation in time attributable to movement of the product such as in the case of temporary change of the speed of the conveyor under the influence of, for example, a load imposed on the conveyor or for the convenience of the production, resulting in a problem associated with incapability of discrimination or reduction of the discriminating accuracy. Also, where the information pattern of the products that are placed on respective tables are to be detected while the sensor is moved relative to the products, similar problems occurs when the time deviation occur as a result of the movement of the sensor.